Chisel Sharpening Technique

[bisco1]

I am capable of getting my chisels reasonably sharp, but nothing like the chisels this man who works for Martin. Any ideas on how it's done?
Thanks, Bill

https://youtu.be/Lz-2OL_b-oU

[srick]

Hi Bill - Back when I used to do a fair amount of woodworking, a wonderful sign carver taught me how to get my tools razor sharp - and I mean sharp enough to shave (the back of my hand, never attempted the face!). A razor sharp chisel cuts through wood like butter.

We used a multi-step process, but the secret came down to a few key things:

• Magnification to see your progress
• final stages of polishing using a hard white stone followed by a buffing wheel with Tripoli polish, and then a buffing wheel with jewelers rouge.

Once you get your chisel to that razor level of sharpness, it stays there for a long time, only needing a buffing several times a day to stay there.

Note in this video, he is controlling his cuts by using the chisel upside down, more like a plane. And, that is a very good chisel. So another secret to keeping sharp chisels is purchasing brands with a high degree of hardness. I have a set of Swedish carving chisels and a set of Japanese chisels purchased many years ago. They were worth every penny because I believe the steel is the secret.

I'm sure that there must be a million techniques for sharpening on the net, but the key is knowing what your aiming for - once you get the 'feel', you never forget it.

best,

Rick

[charles Tauber]

Perhaps it would be more productive to describe what you do now that results in your chisels not being as sharp as you'd like. People can then make suggestions for improvement.

Also, what brand and style of chisels do you use?

[Rudy4]

Originally Posted by bisco1

I am capable of getting my chisels reasonably sharp, but nothing like the chisels this man who works for Martin. Any ideas on how it's done?
Thanks, Bill

https://youtu.be/Lz-2OL_b-oU

Scary Sharp?

https://youtu.be/eom0qu5YO94

[bisco1]

Thanks for all the responses. As to the chisels I use, they are a mixture of varied brands: One is an ancient Witherby, one is a German 2 Cherries, one is a Japanese chisel of a brand I can't pronounce, and one is a Hock curved brace chisel. My method is as follows: I use a honing guide set to provide a 30 degree angle. I have used a micro-bevel in the past, but I feel that the straight 30 degree angle is a little better[maybe my imagination]. I first use 3 Dia-Sharp diamond stones--course, fine and extra fine. On a new chisel I would go through those first to flatten the back. If the back is in good shape, I will touch it up later in the process. I go through the 3 diamond stones to do the bevel, then I go to the glass mounted polishing films that Rudy mentions. I skip the courser films as the extra-fine diamond stone leaves it probably about the same as a 2000-3000 grit stone. So it goes from the diamond to a 8000 film to a 14,000 film and finally to a 60,000 grit film. I make a few passes on the back as I go up. Finally, I use a leather strop with green compound[I forget the brand]. They shine like a mirror front and back and are pretty sharp. But not as sharp as the guy at Martin--it looks like he is going through jello. I am sure that his technique is far superior to mine with the years of day-in, day-out practice, but I also think his tool is somewhat sharper as well. Thanks again, Bill

[srick]

Bill - time to get out a good magnifier\microscope and see what the edge looks like. One trick we used to use (without magnification), was to shine a small bright light at the edge... if it looked white at all, that was an indication that the edge was not ‘truly’ sharp.

Best,

Rick

[bisco1]

Thanks Rick, I'll give the a try. Bill

[charles Tauber]

Originally Posted by bisco1

I use a honing guide set to provide a 30 degree angle.

For Western chisels, 30 degrees is pretty "conservative". The shallower the angle, the "sharper" the tool, but the more fragile the edge. For Western chisels, 25 degrees is pretty common for general woodworking on a variety of woods. You might try a shallower angle than 30 degrees. I'd guess, based on the length of the bevel in the video, he might even have less than 25 degrees. If the chisel is only used on softwoods, like spruce bracing, one could easily get away with a 20 degree angle.

I have used a micro-bevel in the past, but I feel that the straight 30 degree angle is a little better[maybe my imagination].

the micro-bevel is 6 of one, half a dozen of the other: not a make it or break it situation.

I first use 3 Dia-Sharp diamond stones--course, fine and extra fine.

Looking at DMT's website, who makes the Dia-Sharp, they state that "extra fine" is equivalent to a 1200 grit. That isn't fine enough for really sharp tools.

...then I go to the glass mounted polishing films that Rudy mentions. I skip the courser films as the extra-fine diamond stone leaves it probably about the same as a 2000-3000 grit stone. So it goes from the diamond to a 8000 film to a 14,000 film and finally to a 60,000 grit film. I make a few passes on the back as I go up. Finally, I use a leather strop with green compound[I forget the brand].

So, you are going from the extra-fine diamond stone, about 1200 grit, to the 8000 film. That should be fine. (I often use a 1000 grit water stone followed by an 8000 grit water stone and can get a very sharp result going no further.)

People can - and have - debated the value-added of going finer than that, such as 14000 and/or 60000.

The leather strop with compound is probably LESS fine than the 60000 grit film and probably "un-does" some of the work done by the 60,000.

They shine like a mirror front and back

That tells you that you have removed scratches and other surface imperfections but doesn't guarantee good geometry, which is required for "really sharp".

On a new chisel I would go through those first to flatten the back.

That is essential for getting a sharp chisel, new chisel or not.


Think for a moment about the overall process of what you are trying to accomplish. You want, ideally, two "flawless" surfaces - flat planes, typically, on a chisel - meeting at a line. The line is your sharpened edge. There are two stages to "sharpening". The first is shaping the surfaces while the second is honing.

Shaping involves removing metal from the surfaces - usually the bevel and/or the back of the chisel - to establish the planes and the angles between them. Removing a relatively large amount of metal is accomplished quicker by using coarser abrasives. Shaping is required only if the edge is severely damaged, or one wants to change the surfaces or their angles. Shaping of the surfaces creates a burr of metal at their intersection (edge). To create a sharp edge, that burr must be removed, an action accomplished during a subsequent stage, honing.

Honing involves removing as little metal as possible to refine and improve the edge at which the surfaces meet. That includes removing the burr formed during shaping. In the case of honing a chisel that has become "dull", that also includes removing the burr created during the first stage of refining those surfaces. Since the aim of honing is to refine the edge at which already established planes meet - rather than to remove metal to re-shape the surfaces - this is accomplished using fine abrasives.

The implication is that one should hone starting with the finest possible abrasive that will get the job done in a "reasonable" time. Many people start at or around 1000 grit, or its equivalent. That provides a good compromise between speed of refining the already-established surface(s) and being fine enough to reduce the effort required to remove the imperfections created by the coarseness of the abrasive.

One of the primary reasons to use a micro-bevel is that one doesn't need to improve the entire surface of the primary bevel each time one hones. Reducing the area that needs to be improved reduces the time and effort required to do so.

For honing, rather than re-shaping, starting at a coarse stone each time one hones removes more metal than needed and adds time to the refinement process needed to remove the imperfections (scratches) the coarse stones introduce.

At the tail end of honing, it seems like you are using "competing" and redundent abrasives, such as the 60000 grit film and the strop with compound. It's a bit like wearing a belt and suspenders.

If the back of your chisel isn't very flat, you can't fully remove the burr that forms while honing, regardless of how fine is the abrasive. Once you get the back of a chisel very flat, you don't want to touch it again. The only reason to touch it is to remove the burr that is formed along the edge during early stages of honing. Once flattened, I never touch the back of the chisel on anything less than 8000 (or equivalent) grit. It is possible to remove the burr using a leather strop and never touch the back surface of the chisel.

Just as a point of reference, it takes as little as two minutes to hone to razor sharpness an already well-shaped chisel. Sharpening is typically a means to an end, rather than an end in itself: the more time it takes to sharpen one's tools, the less time one spends actually using the tools for their desired purpose.

[srick]

Charles - that was an excellent summary. Every step of the process is important and once you get that edge, it stays for a long time. That’s why I love magnification. You can evaluate the progress of every step and (ahem) ‘hone’ your technique. IMO, the diamonds are excellent abrasives, but they do not have any leeway. 1200 grit is 1200 grit. When you use a conventional stone or sandpaper, the abrasive may range from say 1100-1300 with the average at 1200. Also, with use, some of the conventional abrasive will break down into a finer slurry - this ‘eases’ you to the next level of fineness.

Burs are a constant annoyance and this is where the buffing wheel comes into play. I have found it better than a strop at removing the bur.

Bill, see what the ‘Fine Woodworking Magazine’ archives have to say on the subject. It’s a perennial topic.

Best,

Rick

[mirwa]

Originally Posted by bisco1

I am capable of getting my chisels reasonably sharp, but nothing like the chisels this man who works for Martin. Any ideas on how it's done?
Thanks, Bill

https://youtu.be/Lz-2OL_b-oU

All my chisels are easily that sharp, a blunt chisel is a dangerous tool.

I learnt a long time ago how to sharpen my tools from router bits to scissors, so much easier to carve and cut

The key IMO to getting a sharp tool is understanding the bur that is created during the process, knowing how to feel for an initial bur and working the edge to maintain the bur albeit smaller and finer is the key to a super sharp tool.

I sharpen a lot off chefs knives, as my daughter is a chef.

Steve

[redir]

I use a 10x loop to spy in in how sharp the edge is. Very handy to have. I bought a Marple's chisel some 25 years ago from a good woodworking supply place and the very knowledgeable proprietor of the ship sharpened it for me. It was an absolute dream to use and honestly I've never been able to obtain that level of quality again myself. But I am able to get it to where I can shave hairs on the back of my arm. In fact that is my test for doneness.

As for leather stropes I now use one where the leather is mounted to a flat board. I like the control that has. Once I am good and sharp I use the stripe to put the edge back on many times before going back to the stones.

Lot's of ways to get this job done. Sounds to me like your process is good and that you just need to stick to it and get better.

[bisco1]

Thanks to everyone for all your replies! Charles, thanks for taking the time to give such a detailed and helpful response. Rick, I'll see what I can dig up as far as a magnifier--that should help in evaluation. I have a old Sheffield chisel that I am going to experiment with as far as reducing the angle of the bevel to see if that helps. And, I will keep practicing--it is helpful to know what is possible, it gives one something to shoot for. Bill